The present invention relates to the technical field of internal combustion engines and is aimed more particularly at systems for the direct injection of a fuel into a combustion chamber of a cylinder of a control-ignition or diesel internal combustion engine.
In the conventional way, a system for the direct injection of fuel comprises a controlled fuel injector capable of conveying the fuel directly into the combustion chamber of a cylinder, via an injector of greater or lesser complexity able to withstand the flame front and able directly to withstand combustion. Now, it has become advantageous to use natural gas in direct injection systems by way of a replacement fuel.
The benefit of the use of natural gas in controlled-ignition engines is well known from the viewpoint of overall emissions of pollutants and carbon monoxide. Even partial combustion of natural gas does not lead to the production, in significant quantities, of toxic chemical compounds or of sooty particles. Moreover, natural gas has a very high octane number making it possible for natural gas to be used in all naturally-aspirated or supercharged controlled-ignition engines without any modification. The use of natural gas thus makes it possible to significantly increase the compression ratio or the boost ratio for protection against pinging or against pre-ignition which is far greater than with gasoline or even with other liquefied gases.
It thus seems advantageous to replace the gasoline or liquefied gas supply to the engine with a system for the direct injection of natural gas without reducing the reliability of the engine and at the same time enjoying the ensuing increase in the compression ratio to improve the efficiency and power of the engine.
Many systems for the direct injection of a natural gas intended to be mounted on a combustion engine exist in the state of the art. However, the known technical solutions entail making significant modifications to the cylinder head of the engine delimiting the combustion chamber. In addition, such injection systems generally have a relatively complex design exhibiting a high cost.
One object of the invention is therefore to propose a device for the direct injection of a fuel other than the one initially intended while at the same time being designed to be mounted in place of a spark plug or of the injector in a diesel engine, so as not to entail substantial modifications to the engine.
In order to achieve such an objective, the device according to the invention comprises:
an adapter support intended to be mounted on the cylinder head of the engine, the adapter support being arranged to delimit, on the one hand, at least partially, an injection circuit for the fuel and, on the other hand, a central passage for mounting the spark plug,
and at least one controlled injector for the fuel and one controlled injector for a rinsing gas, the controlled injectors being mounted outside the combustion chamber, so that their outlets are connected to the inlet of the injection circuit.
The device according to the invention also makes it possible to inject a fuel directly into a combustion chamber of a cylinder of a controlled-ignition or diesel internal combustion engine using conventional injectors customarily used for indirect injection.
One object of the invention is also to propose a technique allowing complete injection of the fuel into the combustion chamber of a cylinder of a combustion engine.
To achieve such an objective, the device according to the invention comprises control means making it possible, for each compression stroke, and after the air intake port has closed, to drive:
the fuel injector so as to inject fuel into the combustion chamber and through the injection circuit so as to leave a determined length of time between the end of injection of the fuel and the point of ignition,
the injector of the rinsing gas so as to inject a rinsing gas through the injection circuit at least during the period of time so as to drive the fuel along and convey it into the combustion chamber with a view to it burning in said chamber.
The direct injection device according to the invention is designed to, on the one hand, ensure complete combustion of the fuel inside the combustion chamber and, on the other hand, inject a fuel other than the one initially intended while at the same time not entailing major modifications to such an engine.